I see you've put alot of thought into this!
Where do I see him ending up? Well, apparently Wigan have the first option to sign him as part of the loan deal, he says he loves it at Wigan and they are an improving team with a good chairman and coach. I believe he will probably end up at Wigan personally, if not then Liverpool.
As for Chelsea's formation next year, we need to set up to our strengths - the midfield. If Lampard, Deco, Ballack and Essien are all fit then how do they fit in the team? Mikel is pretty much nailed on to be the holding midfielder and there's no way Lampard will miss out. I think the back 4 and keeper will remain the same with Mikel, Lampard and either Ballack/Essien in midfield with Deco on the left of a front 3, Joe Cole on the right and a big front man up top like Fabiano, Benzema, Huntelaar if Drogba's injuries don't go away, if they do then Drogba will start as number 1.
It's pretty much the same idea/side that played Portsmouth on the first day of the season when everyone (except Drogba and Essien) were fit. It looks like thats the way Scolari wants to do things and I can't see him making too many new buys in the windows (a striker for sure like you say, but I don't think he'll start ahead of Drogba at first). In that game Deco didn't play like a typical winger, he drifted wherever he wanted so was basically just an extra midfielder along with Lampard and Ballack.. that allowed Joe Cole to move in and act as more of a second striker (as you suggested).
So yeah, I can't see many formation or personnel changes happening for a while. When everyone is fit (which is rare with the 2-3 games a week + Internationals) then it'll be pretty close to the first day of the season, when there are injuries then we'll see something similar to what we have now with the 2 more conventional wingers. It all comes down to the big guns in the centre of midfield.